breadcast/breadcast-core/src/dlna/session.rs

use anyhow::{Context, Result};
use rupnp::Service;

use super::device::DlnaDevice;
use super::AV_TRANSPORT;

/// A connected UPnP `AVTransport` control point for a single DLNA media
/// renderer.
///
/// Unlike [`CastSession`](crate::CastSession), there is no persistent
/// connection or background thread to manage here: every UPnP action is an
/// independent SOAP-over-HTTP request, so `DlnaSession` is just a cheap,
/// `Clone`-able handle to the renderer's resolved control endpoint.
/// Concurrent `load()`/`stop()` calls are naturally safe — each is its own
/// HTTP request — with none of the single-socket message-demultiplexing
/// hazard `CastSession` has to run an actor thread to avoid for CASTV2.
#[derive(Clone)]
pub struct DlnaSession {
    device_url: rupnp::http::Uri,
    service: Service,
}

impl DlnaSession {
    /// Fetches `device`'s full description and resolves its `AVTransport`
    /// service. Fails if the device no longer answers, or turns out not to
    /// expose `AVTransport` after all — shouldn't happen given discovery
    /// already searched for exactly that service, but a device's
    /// description can in principle change between being found and being
    /// connected to.
    pub async fn connect(device: &DlnaDevice) -> Result<Self> {
        let device_url: rupnp::http::Uri = device
            .url
            .parse()
            .with_context(|| format!("invalid device description URL: {}", device.url))?;

        let full_device = rupnp::Device::from_url(device_url.clone())
            .await
            .with_context(|| format!("failed to fetch device description from {}", device.url))?;

        let service = full_device
            .find_service(&AV_TRANSPORT)
            .with_context(|| format!("{} has no AVTransport service", device.friendly_name))?
            .clone();

        Ok(Self { device_url, service })
    }

    /// Sets `content_url` as the renderer's current transport URI and
    /// starts playback.
    ///
    /// `content_url` is XML-escaped before being embedded in the SOAP
    /// request body — in breadcast's own usage it's always a URL this
    /// process generated itself (safe by construction), but nothing about
    /// this function's signature guarantees that stays true for every
    /// caller, and an unescaped `&` alone would produce malformed XML the
    /// renderer would reject with no useful diagnostic.
    pub async fn load(&self, content_url: &str) -> Result<()> {
        let escaped = xml_escape(content_url);
        let set_uri_payload = format!(
            "<InstanceID>0</InstanceID><CurrentURI>{escaped}</CurrentURI><CurrentURIMetaData></CurrentURIMetaData>"
        );
        self.service
            .action(&self.device_url, "SetAVTransportURI", &set_uri_payload)
            .await
            .context("SetAVTransportURI failed")?;

        self.service
            .action(&self.device_url, "Play", "<InstanceID>0</InstanceID><Speed>1</Speed>")
            .await
            .context("Play failed")?;

        Ok(())
    }

    /// Stops playback. Unlike `CastSession::stop`, there's no persistent
    /// session or launched app to tear down — this is just the `Stop`
    /// action.
    pub async fn stop(&self) -> Result<()> {
        self.service
            .action(&self.device_url, "Stop", "<InstanceID>0</InstanceID>")
            .await
            .context("Stop failed")?;
        Ok(())
    }

    /// Polls `GetTransportInfo` and returns the renderer's own reported
    /// `CurrentTransportState` (e.g. `"PLAYING"`, `"TRANSITIONING"`,
    /// `"STOPPED"`, `"NO_MEDIA_PRESENT"`).
    ///
    /// This is a request/response poll, not a push subscription —
    /// `AVTransport` does support UPnP eventing (`Service::subscribe` in
    /// `rupnp`) for state pushed as it changes, but that needs a locally
    /// bound HTTP callback listener, which is more machinery than a status
    /// check is worth for now. A caller that wants live updates polls this
    /// on an interval instead.
    pub async fn transport_state(&self) -> Result<String> {
        let response = self
            .service
            .action(&self.device_url, "GetTransportInfo", "<InstanceID>0</InstanceID>")
            .await
            .context("GetTransportInfo failed")?;
        response
            .get("CurrentTransportState")
            .cloned()
            .context("GetTransportInfo response had no CurrentTransportState")
    }
}

fn xml_escape(input: &str) -> String {
    let mut escaped = String::with_capacity(input.len());
    for c in input.chars() {
        match c {
            '&' => escaped.push_str("&amp;"),
            '<' => escaped.push_str("&lt;"),
            '>' => escaped.push_str("&gt;"),
            '"' => escaped.push_str("&quot;"),
            '\'' => escaped.push_str("&apos;"),
            other => escaped.push(other),
        }
    }
    escaped
}